Internal perimeter molding method and related article

ABSTRACT

A two-piece assembly with an internal attachment mechanism includes a tray providing a tray channel and a lid providing a lid channel. The lid is mateable to the tray such that their respective channels combine to form a duct. A bonding material is received in the duct such that the tray and the lid are bonded to one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. Provisional Application Ser. No. 60/857,822 filed Nov. 10, 2006, which is incorporated herein by reference.

TECHNICAL FIELD

The present invention generally relates to the joining of thermoplastic parts. More particularly, the present invention relates to creating an internal leak-free joint between two thermoplastic parts. More specifically, the present invention relates to at least two thermoplastic parts that form a molded-in channel adjacent to their mating surfaces, such that when they are assembled, molten plastic can be injected into the channel creating a leak-free joint between the parts.

BACKGROUND OF THE INVENTION

There is a need to join two thermoplastic parts together. It is well established that thermoplastic parts can be joined by plastic welding. Hot plate and vibration welding are two other examples of plastic welding commonly used in the art. However, these technologies are susceptible to defects relating to appearance, reliability, leakage, and flash. As will be appreciated, molding flash is unsightly and costly to remove.

A common application of thermoplastic joined parts is within the automotive industry. Such parts include sun visors, door panels, air induction systems, and heater assemblies. Often, thermoplastic parts are visible to customers who desire a clean finished appearance of the part. If the thermoplastic part has a displeasing appearance, the part can be rejected either by the auto manufacturer or by the final customer. Automotive HVAC systems and air induction systems require components to be leak-free in order to achieve optimum performance. A thermoplastic component that is defective can contribute to poor performance within its respective system.

Consequently, there is a need in the art for an improved thermoplastic joint that exhibits a clean finished appearance and leak-free properties. Such a thermoplastic produced part should significantly prevent defects in performance and appearance, thus reducing defects in the manufacturing process and return of faulty parts under warranty.

SUMMARY OF THE INVENTION

In light of the foregoing, it is a first aspect of the present invention to provide an internal perimeter molding method and related article.

Another aspect of the present invention is to provide an assembly comprising a tray providing a tray channel, a lid providing a lid channel, wherein the lid is mateable to the tray such that the respective channels combine to form an assembly duct, and a bonding material received in the assembly duct such that the tray and the lid are bonded to one another.

Yet another aspect of the present invention is to provide an assembly comprising a first component providing a first channel, a second component providing a second channel, wherein the first component is mateable to the second component such that the respective channels combine to form an assembly duct, and a bonding material received in the assembly duct such that the first and second components are bonded to one another.

Still another aspect of the present invention is to provide a method for forming an assembly with at least two components, the method comprising assembling at least two components to one another wherein a duct is formed between said at least two components, and injecting a bonding material into the duct, wherein the bonding material secures the at least two components to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings, wherein:

FIG. 1 is a perspective view of an assembly according to the present invention;

FIG. 2 is a cross-sectional view of a tray used in the assembly according to the present invention;

FIG. 3 is a cross-sectional view of a lid used in the assembly according to the present invention;

FIG. 4 is a cross-sectional view of the tray and lid assembled to one another prior to a molding process;

FIGS. 5 A-F are cross-sectional views taken along line 5-5 of FIG. 1 showing alternative tray and lid mating perimeters employable in the present invention;

FIG. 6 is a perspective view of the completed assembly with the lid partially broken away;

FIG. 7 is a top perspective view of the assembly received in a mold showing a fill duct; and

FIG. 8 is a cross-sectional view of the assembly after the molding process.

BEST MODE FOR CARRYING OUT THE INVENTION

An assembly according to the present invention is generally designated by the numeral 10 in the accompanying drawings. The assembly 10 is composed of a thermoplastic material, which may be, but is not limited to polypropylene. Of course, other thermoplastic materials could be used for the assembly 10, as long as the thermoplastic materials employed in the various components are chemically compatible to provide sufficient chemical bonding between the components.

As seen in the drawings, assembly 10 includes a lid generally designated by the number 12 and a tray generally designated by the number 14. The lid 12 and the tray 14 are mateable with one another. The present invention is not limited to the mating of lid to tray, but can also relate to the mating of any two component parts to one another. Although only two component parts—the lid and the tray—are shown bonded, it will be appreciated that other embodiments with properly configured components could allow more than two components to be joined together.

The tray 14 includes a base 16 and side walls 18 which extend from the base. Each side wall 18 provides a flange 20. The base 16 and side walls 18 can form a cavity 19 as shown or can be a solid object. The base 16, which can be any shape, is adjoined to side walls 18 forming an angle between base 16 and side wall 18. The angle between base 16 and sidewall 18 can be just about any angle. And the angle may vary between each side wall 18 to base 16. The flange 20 is shown extending outwardly from side walls 18; however, the flange 20 may extend inward. The flange 20 may include a locating rib 24 which is positioned on a side of the flange opposite the side wall 18 to align tray 14 to lid 12 as will be discussed later. FIG. 2 shows locating rib 24, but other locating features such as a notch, marking, pins, nubs or other alignment registration features could be used. The flange 20 further includes a tray channel 26. In the preferred embodiment, tray channel 26 is shown as semi-circular in shape, but can consist of any geometry. Tray channel 26 provides a channel surface 28. Taken together, the locating rib 24, the tray channel 26, and their associated and adjacent surfaces, if provided, form a tray mating perimeter designated generally by the numeral 30.

The lid 12, as seen in FIG. 3, includes a generally planar top 32, although any curved or curvilinear shape could be employed. Lid 12 is not limited to being a flat surface, and can also have side walls similar to those provided by tray 14. Lid 12 may have a support boss 34 or a rib or other lattice supporting structure to strengthen and prevent deformation of lid 12. A lid flange 36 extends from an underside of the top 32 in a generally downward direction. Top 32, which can be any shape, has a lid mating perimeter 38 as part of its composition. The lid mating perimeter 38 can be located on an outer edge of the top 32, as shown in FIG. 3, or can be positioned anywhere on the top 32, such that it is aligned with the tray mating perimeter 30 when lid 12 and tray 14 are mated together.

Lid flange 36 is positioned along an edge of the top 32, but is not positionally limited to the edge and can be positioned anywhere on the top 32. The flange 36 includes a locating notch 40 that is positioned on the side of the flange to align with locating rib 24 when tray 14 and lid 12 are assembled together. FIG. 3 shows locating notch 40, but the present invention may apply other means such as rib, marking, or no alignment means. In the preferred embodiment, lid channel 42 is shown as semi-circular, but can be any geometry. Lid channel 42 does not have to exist as long as tray channel 26 exists on tray 14. Likewise, tray channel 26 does not have to exist as long as lid channel 42 is provided by the lid 12. Lid channel surface 44 is the perimeter surface of the lid channel 42. Indeed, the lid mating perimeter 38 comprises the lid channel 42, the locating notch 40 and their associated and adjacent surfaces.

As best seen in FIGS. 4, tray 14 and lid 12 are assembled together and positioned adjacent one another by virtue of the rib 24 being received in the notch 40. This mating of the rib and notch 40 temporarily secures the tray and lid to one another. Examples of alternative geometries that may be employed to the tray channel 26, lid channel 42, rib 24 and notch 40 are shown in FIG. 5. This is done in such a manner that the tray channel 26 and the lid channel 42 form an assembly duct 46. As shown in the drawings and more particularly FIG. 6, assembly duct 46 is a continuous path surrounding the perimeter of the assembly providing a leak-free seal. In an alternative embodiment, the assembly duct 46 can extend a partial distance about the perimeter of the assembled components in applications not requiring a leak-free seal. As seen in FIG. 6, both the tray 14 and the lid 12 provide respective channels 26 and 42 that extend to respective edges of their corresponding parts. A fill knob 50 is provided at the respective edges of the tray 14 and the lid 12, wherein the knob 50 has a fill duct 52 extending therethrough that is contiguous with the assembly duct 46.

In some embodiments, as shown in FIG. 7, the assembled pieces may be treated with a bonding agent or material that will enhance bonding of the materials or untreated. Next, the pieces are placed between halves or sections of an injection mold 48 at room temperature. In alternative embodiments, the lid 12 can be treated and preheated before being placed in the injection mold 48. As shown in FIG. 7, the mold has a runner system 49, which aligns with assembly's fill knob 50.

Fill knob 50 extends from the assembled lid and tray and the fill duct 52 includes geometry aligned with an injection mold's nozzle (not shown). In one embodiment the assembly 10 includes a single fill knob 50; however there could be multiple fill knobs 50 extending from the assembly 10 by applying the techniques described herein. Fill knob 50 includes a fill duct 52. Fill duct 52 is contiguous with the assembly duct 46 and provides an entrance point for bonding material 54 to be received. Fill knob 50 can consist of two pieces, tray extension 56 of tray channel 26 and lid extension 58 of lid channel 42, as shown in FIG. 6, or the knob 50 can be a single piece exclusive to either tray 14 or lid 12.

As shown in FIGS. 7 and 8, bonding material 54 is heated to a liquid state and is injected into the mold 48 through the runner system 49 and into ducts 52 and 46. As will be appreciated by skilled artisans, the lid and tray are held in place by the mold sections so as to allow filling of the ducts 46 and 52 with polymeric bonding material. In the present embodiment the bonding material 54 may be polypropylene which is chemically similar to the materials used in the lid and the tray, and is heated between the range of about 450 to about 520 degrees Fahrenheit. In some embodiments, the polypropylene material may be glass-filled. The bonding material 54 has a low viscosity and is forced through the runner system 49 at a relatively low pressure in order to avoid overflow of the bonding material. In one embodiment, the pressure employed is between about 100 to 200 PSI. Bonding material 54 flows through and completely fills the ducts 52 and 46. Assembly 10 is cooled causing bonding member to solidify and join the lid and the tray to one another. In other words, injection of the molten bonding material, which is likely similar to the materials used in forming the lid and the tray, causes the material of the lid and tray in the area surrounding the channels 26 and 42 to also enter a molten condition. The molten condition of materials associated with the lid, the tray and bonding material results in a chemical and mechanical bonding between the component parts and, as the molten material cools, an integral bond between the component parts is formed. It should be noted that any excess gases created by the molding process may vent between a gap formed between the tray channel 26 and lid channel 42 or the entrapped air may naturally vent between the parts.

An assembly, as shown, is believed to have a cycle time between about 30 to 50 seconds. In one embodiment, the assembly is held into position, and is cooled by room temperature. It is also contemplated that other cooling methods can be employed to further reduce overall process time. Upon completion of the molding cycle, the assembly 10 is removed from the injection mold.

The present invention provides advantages in appearance, reliability, leakage, and flash over the prior art of plastic welding. The improvements are achieved through a novel method of joining two or more parts together internally, thus eliminating the requirement of plastic welding. The present invention should significantly prevent manufacturing defects, and reduce the return of nonconforming parts under warranty. The present invention can be implemented at a low cost, because the component parts are connected to one another with similar materials and without any other fastening devices.

Thus, it can be seen that the objects of the invention have been satisfied by the structure and its method for use presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto and thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims. 

1. An assembly comprising: a tray providing a tray channel; a lid providing a lid channel, wherein said lid is mateable to said tray such that said respective channels combine to form an assembly duct; and a bonding material received in said assembly duct such that said tray and said lid are bonded to one another.
 2. The assembly as set forth in claim 1, further comprising: said tray having a tray locator proximate to said tray channel; and said lid having a lid locator mateable to said tray locator, wherein said locators align with one another as said tray and said lid are assembled together.
 3. The assembly as set forth in claim 1, further comprising: a fill knob provided by at least one of said tray and said lid, said fill knob having a fill duct contiguous with said assembly duct for said bonding material to enter said ducts.
 4. The assembly as set forth in claim 2, wherein said tray locator is a rib projecting outward from said tray and said lid locator is a notch.
 5. The assembly as set forth in claim 1, wherein said assembly duct is a continuous path surrounding the perimeter of the assembly.
 6. The assembly as set forth in claim 1, wherein said bonding material is similar to materials used in said lid and said tray.
 7. The assembly as set forth in claim 1, wherein said tray has a base, side walls extending from said base, and a tray flange extending outwardly from the upper ends of said sidewalls; said lid has a generally planar top and a lid flange mateable to said tray flange and extending outwardly from said top; and said channels are positioned within said flanges.
 8. The assembly as set forth in claim 7, wherein said tray flange has a tray locator proximate to said lid channel; and said lid flange having a lid locator mateable to said tray locator and positioned to align with said tray locator when said flanges are assembled together.
 9. The assembly as set forth in claim 1, wherein said lid having a generally planar top, and said tray having an open structure formed from a base and side walls extending from said base.
 10. An assembly comprising: a first component providing a first channel; a second component providing a second channel, wherein said first component is mateable to said second component such that said respective channels combine to form an assembly duct; and a bonding material received in said assembly duct such that said first and second components are bonded to one another.
 11. The assembly as set forth in claim 10, further comprising: said first component further comprising a first locator proximate to said first channel; and said second component having a second locator mateable to said first locator, wherein said locators align with one another as said first and second components are assembled together.
 12. The assembly as set forth in claim 10, further comprising: a fill knob provided by at least one of said first and second components, said fill knob having a fill duct contiguous with said assembly duct for said bonding material to enter said ducts.
 13. The assembly as set forth in claim 10, wherein said bonding material is similar to materials used in said first and second components.
 14. A method for forming an assembly with at least two components, the method comprising: assembling at least two components to one another wherein a duct is formed between said at least two components; and injecting a bonding material into said duct, wherein said bonding material secures said at least two components to one another.
 15. The method according to claim 14, further comprising: placing said at least two components in a mold prior to said bonding material being injected into said duct.
 16. The method according to claim 15, further comprising: using said bonding material that is similar to materials used for manufacturing said at least two components.
 17. The method according to claim 16, further comprising: heating said bonding material to a temperature sufficient to melt material of said at least two components proximal said duct.
 18. The method according to claim 17, further comprising: allowing said heated bonding material and said at least two components to cool such that the assembly is integrally formed.
 19. The method according to claim 15, further comprising: providing said at least two components with a fill knob having a fill duct extending therethrough which is contiguous with said formed duct, said fill duct receiving said bonding material.
 20. The method according to claim 14, further comprising: providing said at least two components with alignment locators mateable with one another. 